Near Earth's surface, on what does the field exert that 9.8 N?
On the Moon, an Apollo astronaut held out a hammer and a feather and let go of both at once. With no air in the way, they hit the ground together.
This lesson explains why everything at one place in a gravitational field speeds up at the same rate, whatever its mass.
Two facts you already have do all the work. From the forces topic: an object's acceleration is the net force on it divided by its mass, a = F/m.
And from this topic: the field exerts the same force on every kilogram. Where g is 1.6 N/kg, each kilogram feels 1.6 newtons.
Put the two together for any falling object. A heavier object feels a larger force: twice the mass means twice the force.
Osei says the Moon's field pulls a 2 kg rock with twice the force it pulls a 1 kg rock. Is he correct?
But a heavier object is also harder to accelerate: twice the mass needs twice the force for the same acceleration.
The two effects cancel exactly. Divide the field's force by the object's mass, and the mass drops out. The acceleration is just g.
On the Moon, g = 1.6 N/kg. A 2 kg rock is dropped. Calculate its acceleration.
Write down the values in the question:
The field exerts 1.6 N on each kilogram, so F = 2 × 1.6 = 3.2 N
m = 2 kg
a = ?
Write down the equation:
a = F/m
Substitute in the values:
a = (3.2)/(2)
Simplify:
a = 1.6 m/s²
The acceleration matches the field strength: 1.6 N/kg of field gives 1.6 m/s² of acceleration.
Beside the rock, a 10 kg boulder is dropped. Calculate its acceleration.
Write down the values in the question:
F = 10 × 1.6 = 16 N
m = 10 kg
a = ?
Write down the equation:
a = F/m
Substitute in the values:
a = (16)/(10)
Simplify:
a = 1.6 m/s², the same acceleration as the 2 kg rock.
An astronaut drops a wrench and a glove together on the airless Moon. Which speeds up faster?
On Earth you rarely see this, because air drags on light, wide objects like feathers. Remove the air, and the Moon demonstration happens: everything falls together.
You met this fact in the motion topic: free fall is independent of mass. Now you have its reason.
Viktor says a 10 kg ball falls faster than a 1 kg ball in a vacuum. Is he correct?
In a vacuum chamber, a steel ball and a ping-pong ball dropped together land together. Which statement explains why?
On Mars, a 6 kg rock in free fall feels a gravitational pull of 22.2 N. Enter its acceleration, in m/s².
On airless Mercury, a lander drops a camera (0.5 kg) and a battery (5 kg) from the same height. What happens?